这项工作的资金由 DNI7 & 赌博公司和美国化学学会石油研究基金 (54462-) 提供。对美国化学学会石油研究基金的捐助者的承认是对这项研究的部分支持。作者想感谢马可 Caggioni 博士的有益讨论。

1. 微流控装置的制作
<ol><li>微流控邮票制作。 注: 此步骤要求使用挥发性材料, 应在化学油烟机中进行。<ol>
<li>使用带有与玻璃幻灯片 (75×50 mm) 相同尺寸的负打印设计、彩色白色的通道和背景色黑色 (请参见图 1)。在透明醋酸板材上打印此设计 (透明度), 分辨率为 1200年 dpi。</li>
		<li>如果透明度的黑暗部分仍然允许光通过, 层数底片和坚持使用双面胶带。</li>
		<li>打开高强度紫外线 (UV) 光源, 使其预热至恒定输出 (约30分钟)。 注: 使用高强度紫外线光源时应佩戴紫外线防护眼镜。</li>
		<li>用丙酮、乙醇和蒸馏水填充三150毫升培养皿。</li>
		<li>在靠近高输出紫外线源的平坦表面上放置一个空白透明度, 但不能直接在 uv 光下。这将提供一个基地, 以制造微流控印章。</li>
		<li>勾勒出 75 x 50 毫米玻璃幻灯片的角落, 在空白透明的中心使用一个永久性的标志, 并放置四玻璃间隔 (约 30 x 30 x 1 毫米) 在轮廓矩形的角落。</li>
		<li>倒入大约5毫升的 UV 固化硫醇: 烯树脂在垫片的中心, 然后小心地放置一个 75 x 50 x 1 毫米玻璃幻灯片上的玻璃隔板, 使胶水完全覆盖的玻璃幻灯片没有气泡。</li>
		<li>将透明度与打印的底片放在玻璃滑梯上, 并移动所有上述组件 (从下到上: 空白透明度, 玻璃隔板和 UV 胶水, 玻璃滑动, 和负印刷透明度), 小心拖动空白透明度紫外线光源下。</li>
		<li>允许 UV 光通过底片照射到树脂上并固化。固化时间可以调整以改变通道的高度。四十五年代治愈时间的结果, 通道高度为1毫米, 使用我们的光源。</li>
		<li>将元件移离 UV 源, 并卸下底片印刷透明度和玻璃滑块。用 UV 胶水制作的通道的玻璃滑块现在被称为微流控标记。</li>
		<li>放弃透明度和玻璃垫片。</li>
		<li>将微流控标记浸在丙酮浴中, 然后再用乙醇浴。重复此步骤两次。丙酮会降解 UV 胶, 所以不要在邮票上留下丙酮大于十年代。</li>
		<li>在拿着邮票的同时, 将邮票浸入水中, 用棉签除去其余的反应树脂。不要直接擦除固化的部分, 因为它会使通道粗糙.
</li>
		<li>将邮票放在纸巾上, 并返回紫外线源至少30分钟, 以确保完全固化。</li>
	</ol></li>
	<li>烷成型
	<ol>
<li>将70克的基硅烷碱倒入透明杯中, 并将交联剂添加到基部, 其重量比为1:10。这些是制造商推荐的比率。不要使用玻璃容器.
</li>
		<li>将交联器和底座与金属搅拌器彻底混合;混合物应该是混浊的, 因为包裹的气泡一旦适当混合。</li>
		<li>将其放入真空烤箱中, 并在混合的聚硅烷上拉真空。如果溶液开始从杯中溢出, 则关闭真空, 然后在溢出消退后恢复真空。真空烤箱的总压力无关紧要, 因为真空只会加速脱气过程。离开房间, 直到所有的气泡从混合物中撤离 (大约60分钟)。</li>
		<li>将微流控标记放在一个空的150毫米直径塑料培养皿中, 然后慢慢地将其倒入培养皿中, 完全覆盖微流控标记。接近培养皿的表面, 以最小化的泡沫重整在。</li>
		<li>覆盖培养皿和放置在一个55摄氏度烤箱过夜治疗。一旦完全治愈, 用刀子切割图案的, 并从邮票中删除。为构建溶剂盆地 (协议步骤 1.6.3) 和 (协议步骤 2.2.1.1) 保留多余的。</li>
		<li>使用0.5 毫米活检冲床, 在以下位置切割孔: 一个在每个角落, 一个在靠近通道边缘的吸入室中, 六在样品室对称地放置的, 和一个在样品室的中心。为了确保对称放置的孔打印一张纸上的图案和在样品室下的地方。由于这是明确的, 你可以很容易地看到孔需要放置。</li>
	</ol></li>
	<li>微流控装置中制造玻璃壁的溶胶-凝胶溶液的制备
	<ol>
<li>在100毫升罐中, 加入25毫升90% 乙醇, 25 毫升 pH 值 4 (0.0001 米) 盐酸溶液, 25 毫升 98% tetraethoxysilane, 25 毫升 98% methyltriethoxysilane。放置100毫升溶液, 现在称为 preconverted 流体, 在微波发现10秒, 然后放置在80°c 过夜。</li>
	</ol></li>
	<li>设备组件
	<ol>
<li>将阵列的两种方法和 75 x 50 x 0.10 毫米玻璃滑入等离子清洗器, 并将3路阀门设置为 off 位置。</li>
		<li>打开真空泵, 允许一分钟疏散房间。</li>
		<li>把3路阀门放在控制器位置, 让房间平衡5秒。流量控制器的位置允许小流量的空气进入等离子清洗器, 低到足以保持室在低压。打开射频 (RF) 开关到介质40秒钟, 然后关闭 RF 开关和真空泵。</li>
		<li>将3路阀门放在打开的位置, 将会议厅返回大气条件。删除阵列和玻璃滑块。</li>
		<li>通过将两个表面相互接触, 仔细地将经过阵列的玻纤片粘贴到玻璃滑梯上。</li>
		<li>在低强度紫外光下, 将紫外光固化树脂应用于有图案的聚甲基丙烯酸酯的接缝上, 固化5分钟。</li>
	</ol></li>
	<li>在微流控通道中制作玻璃幕墙。 注意: 这一步必须在等离子治疗30分钟内完成, 因为它依赖于在等离子处理过程中发生的表面变化。该层的厚度将约为5-10 µm。这一步骤要求使用挥发性材料, 应在化学油烟机中进行。<ol>
<li>设置一个热板到100°c, 并准备四注射器 (三30毫升和一个3毫升) 与18口径针和大约 30 cm 长度的透明热塑性管材。</li>
		<li>分别用乙醇、氯仿和空气填充三30毫升注射器。用 preconverted 液填充一3毫升注射器 (从协议步骤 1.3.1)。</li>
		<li>使用不锈钢连接器将透明热塑性管材插入到阵列中的每个孔中, 除一个角孔外。这个洞将作为一个入口, 而所有其他将是插座。</li>
		<li>用 preconverted 液将微流控装置装入注射器, 然后将微流控装置放在100摄氏度热板上, 使底部玻璃接触热板表面。</li>
		<li>在10秒内通过微流控装置流3毫升的 preconverted 流体。通过改变 preconverted 流体的流速来调整玻璃壁的厚度。</li>
		<li>从热板中取出微流控设备。用空气注射器替换 preconverted 溶液注射器, 并推出任何多余的 preconverted 液。</li>
		<li>用氯仿注射器替换空气注射器, 通过微流控装置慢慢地流动15毫升氯仿。用乙醇注射器取代氯仿注射器, 通过微流控装置缓慢地将30毫升乙醇流动。这些步骤大约需要1分钟。</li>
		<li>用空气注射器替换乙醇注射器, 通过微流控装置流动空气直至干燥。</li>
	</ol></li>
	<li>玻璃支座与溶剂盆的应用
	<ol>
<li>从 75 x 25 x 1 毫米玻璃片中剪下 75 x 10 x 1 毫米的玻璃条。</li>
		<li>将 UV 固化树脂应用于玻璃带上。将微流控装置放到小条上, 并朝上。在低强度紫外线光源下移动5分钟。</li>
		<li>切割 30 x 30 毫米的聚硅烷。使用活检冲床, 切一个足够大的孔, 以覆盖10毫米样品室。</li>
		<li>将该芯片和微流控装置置于等离子清洗器中, 然后将3路阀置于关闭位置并打开真空泵。</li>
		<li>允许一分钟疏散房间。把3路阀门放到流量控制器的位置, 让房间平衡5秒。</li>
		<li>将射频开关转换为介质40秒钟, 然后关闭射频开关和真空泵。</li>
		<li>将3路阀门放在打开的位置, 将会议厅返回大气条件。</li>
		<li>将溶剂盆和微流控装置从等离子腔中取出, 并通过接触表面进行粘附。一定要把溶剂盆放在样品室上。</li>
	</ol></li>
</ol>2. µ2流变过程
<ol><li>
软物质样品的制备
	<ol>
<li>洗涤探针微粒<ol>
<li>吸管水和0.5 µm 探针入一个离心管在水的比率到探针10:1。彻底混合使用吸管混合, 然后将离心管放入离心, 旋转 4600 x g 10 分钟。 注: 本工作中使用的探头溶液在水中悬浮, 初始浓度为2.6% 固体/体积, 样品中所用探针的最终浓度为0.1% 固体/体积。</li>
			<li>取出离心管并取出上清液。用底水代替上清液。重复离心共三次。</li>
			<li>将离心管放在 sonicator 中, 油脂实验低15分钟, 以除去任何骨料。</li>
		</ol>
</li>
		<li>结合探头和软物质。 注: 本程序采用胶体凝胶作为软物质样品。<ol>
<li>在 75 x 50 毫米玻璃滑动, 测量1毫升样品材料。吸管40µL 探针溶液进入样品的中心。</li>
			<li>用金属铲轻轻地折叠样品, 直到完全结合。十五年代将样品舀入离心管中, 离心机在 2340 x g 处去除被包裹的空气。</li>
			<li>用探针/HCO 混合物填充1毫升注射器, 装有18口径针和透明热塑性导管。</li>
		</ol>
</li>
	</ol>
</li>
	<li>
流体交换诱发的连续相变
	<ol>
<li>填充微流控装置<ol>
<li>要创建 1.2.5, 请使用来自协议步骤的过量的来自该组的。使用0.5 毫米直径的活检冲床, 把一个洞中途切到了。将不锈钢接头插入 0.5 mm 直径孔中。</li>
			<li>将热塑性管材连接到拐角入口通道和吸入室出口通道的三。使用连接到设备的注射器将设备完全填满。确保取样室或微流控通道中没有气泡.用硅烷塞子堵住剩余的角孔。</li>
			<li>溶剂盆地应部分填入台阶 2.2.1.2;如果没有填充, 请用清水填满溶剂盆。</li>
			<li>使用该注射器从协议步骤 2.1.2.3, 注入10µL 样品/探针混合物通过中心通道进入样品室约2µL/秒, 然后使用一个注射剂的塞子, 以阻止中心通道在样品室。</li>
		</ol>
</li>
		<li>收集微观流变学数据<ol>
<li>将摄像机设置转换为最优化的, 以尽量减少静态和动态粒子跟踪错误, 然后切换到63×水浸泡目标, 并将水滴滴入透镜。</li>
			<li>将微流控装置置于显微镜阶段, 并提高其目标, 直至其聚焦于样品。</li>
			<li>拍摄探测器的布朗运动的视频, 时间间隔适合于相变的总长度。对于凝胶, 继续拍摄视频, 直到探针运动已完全停止。 注: 我们每10分钟收集一次数据。如果我们从退化实验开始, 就会收集数据直到探针完全扩散。</li>
		</ol>
</li>
		<li>在样品室中交换流体 (重力流动, 用高密度流体交换低密度流体)<ol>
<li>从显微镜阶段取出微流控装置。</li>
			<li>用转移吸管将溶剂盆中的水吸出, 然后将4毫升高浓度流体注入溶剂盆地。</li>
			<li>将微流控装置返回显微镜阶段, 并重复步骤2.2.2。3</li>
		</ol>
</li>
		<li>在样品室中交换液体 (吸入流动, 交换更高密度流体的低密度流体)<ol>
<li>从显微镜阶段取出微流控装置, 并从吸入室中取出该硅烷塞子。</li>
			<li>在吸入室通道内插入装有18口径针和透明热塑性导管的注射器, 并将注射器与注射器泵挂钩。设置注射器泵以1毫升/分钟的拉力。</li>
			<li>在溶剂盆中除去多余的胶凝剂, 用清水冲洗三次, 然后将溶剂盆灌入, 然后吸出冲洗液。</li>
			<li>用注射器泵开始吸入, 同时将水添加到溶剂盆中一分钟。不要让溶剂盆完全空着, 因为这会把空气拉进样品室.
</li>
			<li>将注射器从微流控装置中取出, 并更换吸入腔上的硅烷塞子。</li>
			<li>将微流控装置返回显微镜阶段并继续取样</li>
		</ol>
</li>
	</ol>
</li>
	<li>继续在降解/凝胶循环期间定期取样, 直到所需的周期数完成或测量探头不足。</li>
</ol>

<ol>
	<li>Mitchell, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidics-downsizing+large-scale+biology.">Microfluidics-downsizing large-scale biology.</a> Nat. Biotech. 19, 717-721 (2001).</li><li>Haber, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidics+in+commercial+applications;+an+industry+perspective.">Microfluidics in commercial applications; an industry perspective.</a> Lab Chip. 6, 1118-1121 (2006).</li><li>Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+origins+and+the+future+of+microfluidics.">The origins and the future of microfluidics.</a> Nature. 442, 368-373 (2006).</li><li>Huang, X., Raghavan, S. R., Terech, P., Weiss, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distinct+kinetic+pathways+generate+organogel+networks+with+contrasting+fractality+and+thixotropic+properties.">Distinct kinetic pathways generate organogel networks with contrasting fractality and thixotropic properties.</a> J. Am. Chem. Soc. 128, 15341-15352 (2006).</li><li>Larsen, T. H., Schultz, K. M., Furst, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogel+microrheology+near+the+liquid-solid+transition.">Hydrogel microrheology near the liquid-solid transition.</a> Korea-Aust. Rheol. J. 20, 165-173 (2008).</li><li>Larsen, T. H., Furst, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microrheology+of+the+liquid-solid+transition+during+gelation.">Microrheology of the liquid-solid transition during gelation.</a> Phys. Rev. Lett. 100, 146001 (2008).</li><li>Schultz, K. M., Baldwin, A. D., Kiick, K. L., Furst, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+rheological+screening+to+identify+conditions+of+biomaterial+hydrogelation.">Rapid rheological screening to identify conditions of biomaterial hydrogelation.</a> Soft Matter. 5, 740-742 (2009).</li><li>Switzer, L. H., Klingenberg, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flocculation+in+simulations+of+sheared+fiber+suspensions.">Flocculation in simulations of sheared fiber suspensions.</a> Int. J. Multiph. Flow. 30, 67-87 (2004).</li><li>Wehrman, M. D., Lindberg, S., Schultz, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+the+dynamic+transition+of+hydrogenated+castor+oil+gels+measured+via+multiple+particle+tracking+microrheology.">Quantifying the dynamic transition of hydrogenated castor oil gels measured via multiple particle tracking microrheology.</a> Soft Matter. 12, 6463-6472 (2016).</li><li>Wehrman, M. D., Milstrey, M. J., Lindberg, S., Schultz, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+&#181;2rheology+to+quantify+rheological+properties+during+repeated+reversible+phase+transitions+of+soft+matter.">Using &#181;2rheology to quantify rheological properties during repeated reversible phase transitions of soft matter.</a> Lab Chip. 17, 2085-2094 (2017).</li><li>Wehrman, M. D., Lindberg, S. E., Schultz, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+shear+on+the+structure+and+rheological+properties+of+a+hydrogenated+castor+oil+colloidal+gel+during+dynamic+phase+transitions.">Impact of shear on the structure and rheological properties of a hydrogenated castor oil colloidal gel during dynamic phase transitions.</a> J. Rheol. , (2018).</li><li>Loh, X. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-responsive+"reversible+micelles".">Dual-responsive "reversible micelles".</a> J. Appl. Polym. Sci. 127, 992-1000 (2013).</li><li>Kern, F., Zana, R., Candau, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rheological+properties+of+semidilute+and+concentrated+aqueous+solutions+of+cetyltrimethylammonium+chloride+in+the+presence+of+sodium+salicylate+and+sodium+chloride.">Rheological properties of semidilute and concentrated aqueous solutions of cetyltrimethylammonium chloride in the presence of sodium salicylate and sodium chloride.</a> Langmuir. 7, 1344-1351 (1991).</li><li>Trappe, V., Prasad, V., Cipelletti, L., Segre, P. N., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Jamming+phase+diagram+for+attractive+particles.">Jamming phase diagram for attractive particles.</a> Nature. 411, 772-775 (2001).</li><li>Philipse, A. P., Wierenga, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+density+and+structure+formation+in+gels+and+clusters+of+colloidal+rods+and+fibers.">On the density and structure formation in gels and clusters of colloidal rods and fibers.</a> Langmuir. 14, 49-54 (1998).</li><li>Schultz, K. M., Bayles, A. V., Baldwin, A. D., Kiick, K. L., Furst, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid,+high+resolution+screening+of+biomaterial+hydrogelators+by+mu2rheology.">Rapid, high resolution screening of biomaterial hydrogelators by mu2rheology.</a> Biomacromolecules. 12, 4178-4182 (2011).</li><li>Crocker, J. C., Grier, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+of+digital+video+microscopy+for+colloidal+studies.">Methods of digital video microscopy for colloidal studies.</a> J. Colloid Interface Sci. 179, 298-310 (1996).</li><li>Mason, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+the+viscoelastic+moduli+of+complex+fluids+using+the+generalized+Stokes--Einstein+equation.">Estimating the viscoelastic moduli of complex fluids using the generalized Stokes--Einstein equation.</a> Rheol. Actac. 39, 371-378 (2000).</li><li>Mason, T. G., Ganesan, K., van Zanten, J. H., Wirtz, D., Kuo, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+tracking+microrheology+of+complex+fluids.">Particle tracking microrheology of complex fluids.</a> Phys. Rev. Lett. 79, 3282-3285 (1997).</li><li>Mason, T. G., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+measurements+of+frequency-dependent+linear+viscoelastic+moduli+of+complex+fluids.">Optical measurements of frequency-dependent linear viscoelastic moduli of complex fluids.</a> Phys. Rev. Lett. 74, 1250-1253 (1995).</li><li>Squires, T. M., Mason, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluid+mechanics+of+microrheology.">Fluid mechanics of microrheology.</a> Annu. Rev. Fluid Mech. 42, 413-438 (2010).</li><li>Gittes, F., Schnurr, B., Olmsted, P. D., MacKintosh, F. C., Schmidt, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscopic+viscoelasticity:+shear+moduli+of+soft+materials+determined+from+thermal+fluctuations.">Microscopic viscoelasticity: shear moduli of soft materials determined from thermal fluctuations.</a> Phys. Rev. Lett. 79, 3286-3289 (1997).</li><li>Mai, D. J., Brockman, C., Schroeder, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+systems+for+single+DNA+dynamics.">Microfluidic systems for single DNA dynamics.</a> Soft Matter. 8 (41), 10560-10572 (2012).</li><li>Tanyeri, M., Ranka, M., Sittipolkul, N., Schroeder, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microfluidic-based+hydrodynamic+trap:+design+and+implementation.">A microfluidic-based hydrodynamic trap: design and implementation.</a> Lab Chip. 11, 1786-1794 (2011).</li><li>Lee, J. S., Dylla-Spears, R., Teclemariam, N. P., Muller, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+four-roll+mill+for+all+flow+types.">Microfluidic four-roll mill for all flow types.</a> Appl. Phys. Lett. 90, 074103 (2007).</li><li>Crocker, J. C., Grier, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+of+digital+video+microscopy+for+colloidal+studies.">Methods of digital video microscopy for colloidal studies.</a> J. Colloid Interface Sci. 179 (1), 298-310 (1996).</li><li>Mason, T. G., Weitz, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+measurements+of+frequency-dependent+linear+viscoelastic+moduli+of+complex+fluids.">Optical measurements of frequency-dependent linear viscoelastic moduli of complex fluids.</a> Phys. Rev. Lett. 74 (7), 1250 (1995).</li><li>Schultz, K. M., Furst, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+rheology+in+a+microfluidic+device.">High-throughput rheology in a microfluidic device.</a> Lab on a chip. 11, 3802-3809 (2011).</li><li>Abate, A. R., Lee, D., Do, T., Holtze, C., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glass+coating+for+PDMS+microfluidic+channels+by+sol-gel+methods.">Glass coating for PDMS microfluidic channels by sol-gel methods.</a> Lab Chip. 8, 516-518 (2008).</li><li>Happel, J., Brenner, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Low Reynolds Number Hydrodynamics: with special applications to particulate media. , (1965).</li></ol>

这项工作没有披露。

通过以下经过充分记录的微流控芯片制造技术29, 可以轻松地进行双层微流控设备 (图 1)。在装置的底部添加玻璃支撑, 以减少振动对探针运动的影响。玻璃滑动是非常稀薄的 (0.10 毫米) 为了容纳显微镜目标的工作距离。这使得该设备易受建筑物中的小振动和样品环境的影响, 然后用高速相机测量。玻璃支持成功地抵消了这些外部刺激。选择短工作距离目标, ?...

软物质中的相变可以改变脚手架结构, 这在材料的处理和最终稳定性方面有影响1,2,3。在动态相变过程中, 软材料的表征为结构演化与平衡结构和流变特性之间的关系提供了重要的信息。例如, 许多家庭护理产品需要在消费者使用期间发生阶段性变化。此外, 在生产过程中, 加工步骤, 包括稀释和混合, 可以传递剪切影响的流变性能和最终显微组织的产品。了解整个相变的流变特性, 确保产品按设计进行。此外, 如果力改变材料在制造过程中的开始流变, 相变会产生意想不到的和不希望的结果, 改变预期的功能和效果。在临界凝胶点, 定义为物质从相关胶体或聚合物溶液过渡到样品生成凝胶网络的点, 材料性质随联想的细微变化而急剧变化。在关键凝胶点上对结构的任何修改都会影响最终产品4。在这些动态过渡过程中, 软材料具有弱的机械性能和测量, 使用经典的实验技术可以在测量噪声限制下5,6,7。为此, 在低模量范围 (10-3 -4 Pa) 中敏感的 microrheology 技术被用来表征弱初凝胶在动态演化过程中的特征。有些材料因外力而易受显微组织的变化, 这在表征过程中提出了挑战, 因为任何材料或流体的转移都可能影响结构, 最终材料的性能也会受到冲击。为了避免改变材料的显微结构, 我们开发了一种微流控装置, 可以在试样周围交换环境流体, 同时尽量减少剪切。通过交换流体环境, 在相变过程中测量流变特性和显微组织的变化, 并以最小的剪切贡献。该装置与多粒子跟踪 microrheology (等离子体) 结合在一种称为µ2流变学的技术中。该技术用于在凝胶的连续相变过程中, 对外部驱动力进行定量测定材料性能。该技术将说明使用纤维胶体凝胶, 氢化蓖麻油 (HCO)9,10,11。
凝胶支架由于其示例环境12,13,14,15, 可能会经历联想和离解的变化。胶凝和降解的驱动力是具体的材料, 必须为每个感兴趣的材料量身定做。µ2流变学可用于表征对外部刺激反应的凝胶系统, 包括胶体和聚合网络。改变 pH, 渗透压力或盐浓度是驱动力的例子, 可以引起材料微观结构的变化。例如, HCO 通过创建渗透压力梯度来经历控制的相变。当浓缩的 HCO 凝胶样品 (4 wt% HCO) 淹没在水中时, 胶体颗粒之间的吸引力减弱, 导致降解。或者, 当 HCO (0.125 wt% HCO) 的稀释溶液与亲水性材料 (称为凝胶剂, 主要由甘油和表面活性剂组成) 接触时, 吸引力会返回, 导致凝胶化。此凝胶系统将用于显示设备的操作, 作为测量单个示例9、10上的连续相转换的工具。为了表征这些凝胶支架在动态过渡过程中的特征, 以及在临界相变时的微妙初始凝胶结构, 我们利用等离子体来表征这些材料的高时空分辨率。
Microrheology 是用来确定凝胶的性质和结构, 特别是在关键的过渡, 一系列软材料, 包括胶体和聚合物凝胶5,6,9,16。微波等离子体是一种被动微观流变学技术, 它使用视频显微镜记录在样品中嵌入的荧光探针粒子的布朗运动。整个视频中的粒子位置精确地确定为使用经典跟踪算法17,18的像素的 1/10th 。从这些粒子轨迹计算了集合平均均方根位移 (本, Δr2(t))。该方法与材料性能有关, 如蠕变符合性, 使用广义斯托克斯-爱因斯坦关系17,19,20,21,22, 23。该材料的状态是通过计算该曲线的对数斜率作为滞后时间的函数来确定的, α,
<img alt="Equation 1" src="/files/ftp_upload/57429/57429eq1.jpg">
其中t为滞后时间, 并将其与临界松弛指数 ( n) 进行比较。n是使用时间固化叠加法确定的, 一种记录良好的技术, 它经过拉森和 Furst6进行了修改, 以分析等离子体数据。通过比较n到α材料的状态定量地被确定。当α > n材料为溶胶时, 当α < n材料为凝胶时。以前的工作使用 microrheology 来确定临界松弛指数9的 HCO 系统的特征。使用这些信息, 我们精确地确定在实验中材料何时从凝胶转变为溶胶。此外, 非高斯参数, αNG, 可以计算, 以确定系统的结构异质性的程度,
<img alt="Equation 2" src="/files/ftp_upload/57429/57429eq2.jpg">
其中Δx(t) 是x方向上的一维粒子移动。使用等离子体, 我们可以表征一个单相过渡, 但通过表征材料与微波微流体装置, 我们能够操纵周围的流体环境和收集数据的几个相变的单一凝胶样品。
该微流控装置的设计目的是研究单个凝胶样品的临界过渡, 以响应周围流体环境的变化而进行相变。当该装置在凝胶或溶胶状态下, 通过锁定样品以诱导相变, 同时最小化剪切时, 该设备会交换样品周围的流体。溶剂盆地位于样品室的正上方, 由六个对称间隔的入口通道连接。这种对称性允许液体从溶剂盆地交换到样品室, 同时在样品周围产生同样的压力, 将其锁定到位。已经有几项研究将这种技术用于单粒子和 DNA 捕获, 但这项工作将从单个分子到大约10µL24、25、26的样本量扩展。这种独特的设计还能在相变过程中实现实时的微观流变学特性。
µ2流变学是一种适用于许多软物质系统的健壮技术。本文所描述的技术是为胶体凝胶设计的, 但它可以很容易地适应其他材料, 如聚合物或胶束溶液。利用这一技术, 我们不仅确定了相变对平衡材料性能的影响, 而且还决定了不同加工步骤对材料的流变演化和最终脚手架结构的持久影响, 以及性能。

<table><tbody><tr><td>150 x 15 mm Petri Dish</td><td>Corning, Inc.</td><td>351058</td><td></td></tr><tr><td>75 x 50 x 0.15 mm glass slide</td><td>Fisher Scientific</td><td>Custom</td><td></td></tr><tr><td>75 x 50 x 1.0 mm glass slide</td><td>Fisher Scientific</td><td>12-550-C</td><td></td></tr><tr><td>75 x 25 x 1.0 mm glass Slide</td><td>Fisher Scientific</td><td>12-550-A3</td><td></td></tr><tr><td>22 x 22 Glass cover slips</td><td>Fisher Scientific</td><td>12-542-B</td><td></td></tr><tr><td>Acetone, 99.5%</td><td>VWR Analytical</td><td>67-64-1</td><td></td></tr><tr><td>Low intensity UV source</td><td>UVP</td><td>UVL-56</td><td></td></tr><tr><td>Chloroform, 99.9%</td><td>Fisher Chemical</td><td>C298-500</td><td></td></tr><tr><td>Cotton Swabs</td><td>Q-tips</td><td>83289205</td><td></td></tr><tr><td>Ethanol, 90%</td><td>Fisher Chemical</td><td>A962-4</td><td></td></tr><tr><td>Fluoresbrite&amp;reg; YG Carboxylate Microspheres 0.50&amp;micro;m</td><td>Polysciences, Inc.&amp;nbsp;</td><td>15700-10</td><td></td></tr><tr><td>High-Intensity UV Lamp</td><td>Spectroline Corp.</td><td>SB-100P</td><td></td></tr><tr><td>Hot plate</td><td>Corning, Inc.</td><td>PC-420</td><td></td></tr><tr><td>Hydrochloric Acid, 6N</td><td>Ricca Chemical Company</td><td>3750-32</td><td></td></tr><tr><td>Methyltriethyoxysilane, 98%</td><td>Acros Organics</td><td>174622500</td><td></td></tr><tr><td>Microcentrifuge</td><td>Eppendorf</td><td>5424</td><td></td></tr><tr><td>Plasma cleaner</td><td>Harrick Plasma, Inc.</td><td>PDC-32G</td><td></td></tr><tr><td>Polydimethylsiloxane (PDMS)</td><td>Robert McKwown Company</td><td>2065622</td><td></td></tr><tr><td>Sonicator</td><td>Branson, Emerson Electric</td><td>1800</td><td></td></tr><tr><td>Steel connectors, ID 0.023 inch</td><td>New England Small Tube Corp.</td><td>Custom</td><td></td></tr><tr><td>Tetraethoxysilane, 98%</td><td>Alfa Aesar</td><td>A14965</td><td></td></tr><tr><td>Thiol-ene Resin (UV curable)</td><td>Norland Products, Inc.&amp;nbsp;</td><td>NOA81</td><td></td></tr><tr><td>Transparency</td><td>Staples Inc.&amp;nbsp;</td><td>21828</td><td></td></tr><tr><td>Tygon tubing, ID 1/32 inch</td><td>McMaster-Carr</td><td>E-3603</td><td></td></tr><tr><td>Vacuum oven</td><td>Fisher Scientific</td><td>282A</td><td></td></tr><tr><td>Biopsy punch 8 mm</td><td>World Precision Instruments</td><td>504535</td><td></td></tr><tr><td>Bioposy punch 0.5 mm</td><td>World Precision Instruments</td><td>504528</td><td></td></tr><tr><td>Syringe, 30 mL</td><td>BD</td><td>309659</td><td></td></tr><tr><td>Syringe, 3 mL</td><td>BD</td><td>309651</td><td></td></tr><tr><td>Needle, 18 gauge</td><td>BD</td><td>305195</td><td></td></tr><tr><td>Microcentrifuge tube, 1.5 mL</td><td>Eppendorf</td><td>22-36-320-4</td><td></td></tr><tr><td>High-speed Camera</td><td>Vision Research</td><td>Miro M120&amp;nbsp;</td><td></td></tr><tr><td>Microscope</td><td>Carl Zeiss AG</td><td>Zeiss Observer, Z1</td><td></td></tr><tr><td>Syringe pump</td><td>New Era Pump Systems</td><td>NE-300</td><td></td></tr><tr><td>Hydrogenated castor oil</td><td>Procter &amp;amp; Gamble</td><td>N/A</td><td></td></tr><tr><td>Af&amp;iacute;cio MP 6002 Printer</td><td>Ricoh Company, Ltd.</td><td>415877</td><td></td></tr></tbody></table>

combining microfluidics and microrheology to determine rheological properties of soft matter during repeated phase transitions

软物质的显微结构直接影响宏观流变性能, 可通过在前相变化和应用剪切过程中的胶体重排等因素来改变。为了确定这些变化的程度, 我们开发了一种微流控装置, 它能使周围流体和微观流变学特性的交换引起的重复相变, 同时限制试样的剪切。此技术µ2流变学, 微流体和 microrheology 的组合。微流控装置是两层设计, 其对称入口流进入取样室, 在流体交换过程中捕获凝胶样品。吸力可以应用在远离样品室, 把液体拉入样品室。利用多粒子跟踪 microrheology (等离子体) 对材料的流变性能进行了表征。在微波等离子体中, 荧光探针粒子嵌入到材料中, 探针的布朗运动使用视频显微镜进行记录。对粒子的运动进行了跟踪, 计算了平均平方位移。利用广义斯托克斯-爱因斯坦关系, 该方法与宏观流变性质有关。通过与临界松弛指数的比较, 确定了材料的相位, 并用时间-固化叠加法确定。纤维胶体凝胶的测量表明了该技术的实用性。这种凝胶有一个微妙的结构, 可以不可逆转地改变时, 剪切应用。µ2流变数据表明, 材料在每次相变后反复 equilibrates 到相同的流变性质, 表明相转变在显微结构变化中不起作用。为了确定剪切的作用, 样品可以在注入到我们的微流控装置之前被剪切。µ2流变学是一种广泛适用的技术, 用于对软物质进行表征, 使在相变过程中, 单个样品中微细微结构的流变特性能够得到测定, 以响应周围环境条件。

两层微流控装置是用在微流控标记上进行阵列的 (图 1a、b) 构造的。图章的设计显示在图 1c中。不正确的实验设置会导致在周围流体交换过程中被动 microrheology 和微流控流的错误 (图 2)。在讨论部分中详细介绍了不正确的实验设置示例。在设备操作过程中, 围绕凝胶样品周围的流体...

Watch this Scientific Journal Video about Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions at JoVE.com

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

我们演示了一个微流控装置的制造和使用, 使多粒子跟踪 microrheology 测量, 以研究重复相变的流变效应对软物质。

微流体和 Microrheology 相结合测定软物质在重复相变过程中的流变特性

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement ...

combining-microfluidics-microrheology-to-determine-rheological

Universidad San Sebastian

Research

Education

JoVE Core

JoVE Journal

Physics

Engineering

Unit 1

Temperature and Heat

SCIENTISTS IN ACTION

7.8K 次观看.  Lehigh University. 我们演示了一个微流控装置的制造和使用, 使多粒子跟踪 microrheology 测量, 以研究重复相变的流变效应对软物质。

视频: Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

测量材料在微流使用1-2面流小角中子散射

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

科研

工程学

Synthesis of Poly(N-isopropylacrylamide) Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability

Janus microparticles are compartmentalized particles with differing molecular structures and/or functionality on each of their two sides. Because of this unique property, Janus microparticles have been recognized as a new class of materials, thereby attracting a great deal of attention from various research fields. The versatility of these microparticles has been exemplified through their uses as building blocks for self-assembly, electrically responsive actuators, emulsifiers for painting and cosmetics, and carriers for drug delivery. This study introduces a detailed protocol that explicitly describes a synthetic method for designing novel Janus microhydrogels composed of a single base material, poly(N-isopropylacrylamide) (PNIPAAm). Janus microdroplets are firstly generated via a hydrodynamic focusing microfluidic device (HFMD) based on the separation of a supersaturated aqueous NIPAAm monomer solution and subsequently polymerized through exposure to UV irradiation. The resulting Janus microhydrogels were found to be entirely composed of the same base material, featured an easily identifiable compartmentalized morphology, and exhibited anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability. We believe that the proposed method introduces a novel hydrogel platform with the potential for advanced synthesis of multi-functional Janus microhydrogels.

Synthesis of PolyN-isopropylacrylamide Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability

We present a protocol to synthesize Janus microhydrogels composed entirely of the same base material, poly(N-isopropylacrylamide) (PNIPAAm), with a clearly compartmentalized structure base on the phase separation of a supersaturated NIPAAm monomer solution. The synthesized Janus microhydrogels show unique properties such as anisotropic thermo-responsiveness and organophilic/hydrophilic loading capability.

合成聚（<em&gt;ñ</em&gt; -isopropylacrylamide）剑锋Microhydrogels各向异性热响应能力和亲有机/亲水承载能力

Janus microparticles are compartmentalized particles with differing molecular structures and/or functionality on each of their two sides. Because of this ...

化学

Microfluidic Mixers for Studying Protein Folding

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason for this is that folding takes place over a wide range of timescales, from nanoseconds to seconds or longer, depending on the protein1. Conventional stopped-flow mixers have allowed measurement of folding kinetics starting at about 1 ms. We have recently developed a microfluidic mixer that dilutes denaturant ~100-fold in ~8 &mu;s2. Unlike a stopped-flow mixer, this mixer operates in the laminar flow regime in which turbulence does not occur. The absence of turbulence allows precise numeric simulation of all flows within the mixer with excellent agreement to experiment3-4.
Laminar flow is achieved for Reynolds numbers Re &le;100. For aqueous solutions, this requires micron scale geometries. We use a hard substrate, such as silicon or fused silica, to make channels 5-10 &mu;m wide and 10 &mu;m deep (See Figure 1). The smallest dimensions, at the entrance to the mixing region, are on the order of 1 &mu;m in size. The chip is sealed with a thin glass or fused silica coverslip for optical access. Typical total linear flow rates are ~1 m/s, yielding Re~10, but the protein consumption is only ~0.5 nL/s or 1.8 &mu;L/hr. Protein concentration depends on the detection method: For tryptophan fluorescence the typical concentration is 100 &mu;M (for 1 Trp/protein) and for FRET the typical concentration is ~100 nM.
The folding process is initiated by rapid dilution of denaturant from 6 M to 0.06 M guanidine hydrochloride. The protein in high denaturant flows down a central channel and is met on either side at the mixing region by buffer without denaturant moving ~100 times faster (see Figure 2). This geometry causes rapid constriction of the protein flow into a narrow jet ~100 nm wide. Diffusion of the light denaturant molecules is very rapid, while diffusion of the heavy protein molecules is much slower, diffusing less than 1 &mu;m in 1 ms. The difference in diffusion constant of the denaturant and the protein results in rapid dilution of the denaturant from the protein stream, reducing the effective concentration of the denaturant around the protein. The protein jet flows at a constant rate down the observation channel and fluorescence of the protein during folding can be observed using a scanning confocal microscope5.

In this work we explain the fabrication and use of a microfluidic mixer capable of mixing two solutions in ~8 &mu;s. We also demonstrate the use of these mixers with spectroscopic detection using UV fluorescence and fluorescence resonance energy transfer (FRET).

研究蛋白质折叠的微流体混合器

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason ...

生物工程

Phase Diagram Characterization Using Magnetic Beads as Liquid Carriers

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for the purpose of investigating phase change of those liquid segments. The magnetic beads were externally controlled using a magnet, allowing for the beads to bridge the air valve between the adjacent liquid segments. A hydrophobic coating was applied to the inner surface of the tube to enhance the separation between two liquid segments. The applied magnetic field formed an aggregate cluster of magnetic beads, capturing a certain liquid amount within the cluster that is referred to as carry-over volume. A fluorescent dye was added to one liquid segment, followed by a series of liquid transfers, which then changed the fluorescence intensity in the neighboring liquid segment. Based on the numerical analysis of the measured fluorescence intensity change, the carry-over volume per mass of magnetic beads has been found to be ~2 to 3 &#181;l/mg. This small amount of liquid allowed for the use of comparatively small liquid segments of a couple hundred microliters, enhancing the feasibility of the device for a lab-in-tube approach. This technique of applying small compositional variation in a liquid volume was applied to analyzing the binary phase diagram between water and the surfactant C12E5 (pentaethylene glycol monododecyl ether), leading to quicker analysis with smaller sample volumes than conventional methods.

Here, we present a protocol to investigate multi-component phase diagrams using externally controlled magnetic beads as liquid carriers in a lab-in-tube approach. This approach can aid in applications that seek to gather further information on phase change in complex liquid systems.

相图表征使用磁珠用作液体载体

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for ...

Dielectric RheoSANS &#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and microstructural properties of complex fluids is presented. The instrument consists of a Couette geometry contained within a modified forced convection oven mounted on a commercial rheometer. This instrument is available for use on the small angle neutron scattering (SANS) beamlines at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). The Couette geometry is machined to be transparent to neutrons and provides for measurement of the electrical properties and microstructural properties of a sample confined between titanium cylinders while the sample undergoes arbitrary deformation. Synchronization of these measurements is enabled through the use of a customizable program that monitors and controls the execution of predetermined experimental protocols. Described here is a protocol to perform a flow sweep experiment where the shear rate is logarithmically stepped from a maximum value to a minimum value holding at each step for a specified period of time while frequency dependent dielectric measurements are made. Representative results are shown from a sample consisting of a gel composed of carbon black aggregates dispersed in propylene carbonate. As the gel undergoes steady shear, the carbon black network is mechanically deformed, which causes an initial decrease in conductivity associated with the breaking of bonds comprising the carbon black network. However, at higher shear rates, the conductivity recovers associated with the onset of shear thickening. Overall, these results demonstrate the utility of the simultaneous measurement of the rheo-electro-microstructural properties of these suspensions using the dielectric RheoSANS geometry.

Here, we present a procedure for the measurement of simultaneous impedance, rheology and neutron scattering from soft matter materials under shear flow.

介电RheoSANS  - 阻抗，流变性和复杂流体的小角中子散射的同时拷问

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and ...

Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion co-flow device to generate uniform high-viscosity droplets in a low-viscosity fluid. The microfluidic capillary device has a common co-flow structure with its exit connecting to a wider tube. Elongated droplets of the low-viscosity fluid are first encapsulated by the high-viscosity fluid in the co-flow structure. As the elongated low-viscosity droplets flow through the exit, which is treated to be wetted by the low-viscosity fluid, phase inversion is then induced by the adhesion of the low viscosity droplets to the tip of the exit, which results in the subsequent inverse encapsulation of the high-viscosity fluid. The size of the resultant high-viscosity droplets can be adjusted by changing the flow rate ratio of the low-viscosity fluid to the high-viscosity fluid. We demonstrate several typical examples of the generation of high-viscosity droplets with a viscosity up to 11.9 Pas, such as glycerol, honey, starch, and polymer solution. The method provides a simple and straightforward approach to generate monodisperse high-viscosity droplets, which may be used in a variety of droplet-based applications, such as materials synthesis, drug delivery, cell assay, bioengineering, and food engineering.

A phase-inversion co-flow device is demonstrated to generate monodisperse high-viscosity droplets above 1 Pas, which is difficult to realize in droplet microfluidics.

反相共流微流控毛细管装置制备高粘度水滴的方法

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion ...

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white blood cells and platelets that are suspended in blood plasma. Due to the abundance of the RBCs (40% to 45% of the blood volume), their behavior dictates the rheological behavior of blood especially in the microcirculation. At very low shear rates, RBCs are seen to assemble and form entities called aggregates, which causes the non-Newtonian behavior of blood. It is important to understand the conditions of the aggregates formation to comprehend the blood rheology in microcirculation. The protocol described here details the experimental procedure to determine quantitatively the RBC aggregates in microcirculation under constant shear rate, based on image processing. For this purpose, RBC-suspensions are tested and analyzed in 120 x 60 &#181;m poly-dimethyl-siloxane (PDMS) microchannels. The RBC-suspensions are entrained using a second fluid in order to obtain a linear velocity profile within the blood layer and thus achieve a wide range of constant shear rates. The shear rate is determined using a micro Particle Image Velocimetry (&#181;PIV) system, while RBC aggregates are visualized using a high speed camera. The videos captured of the RBC aggregates are analyzed using image processing techniques in order to determine the aggregate sizes based on the images intensities.

The protocol described details an experimental procedure to quantify Red Blood Cell (RBC) aggregates under a controlled and constant shear rate, based on image processing techniques. The goal of this protocol is to relate RBC aggregate sizes to the corresponding shear rate in a controlled microfluidic environment.

微流控控制环境的红细胞聚集动态调查

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren system is constructed from a Hoffman modulation contrast microscope, which provides easy access to the rear focal plane of the objective lens, by removing the slit plate and replacing the modulator with a knife-edge. The working principle of microscale schlieren technique relies on detecting light deflection caused by variation of refractive index1-3. The deflected light either escapes or is obstructed by the knife-edge to produce a bright or a dark band, respectively. If the refractive index of the mixture varies linearly with its composition, the local change in light intensity in the image plane is proportional to the concentration gradient normal to the optical axis. The micro-schlieren image gives a two-dimensional projection of the disturbed light produced by three-dimensional inhomogeneity.
To accomplish quantitative analysis, we describe a calibration procedure that mixes two fluids in a T-microchannel. We carry out a numerical simulation to obtain the concentration gradient in the T-microchannel that correlates closely with the corresponding micro-schlieren image. By comparison, a relationship between the grayscale readouts of the micro-schlieren image and the concentration gradients presented in a microfluidic device is established. Using this relationship, we are able to analyze the mixing inhomogeneity from associate micro-schlieren image and demonstrate the capability of microscale schlieren technique with measurements in a microfluidic oscillator4. For optically transparent fluids, microscale schlieren technique is an attractive diagnostic tool to provide instantaneous full-field information that retains the three-dimensional features of the mixing process.

Herein, we describe a procedure that employs microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. Through calibration, distribution of concentration gradient can be derived from the micro-schlieren image.

由微型条纹分析技术在微流控设备混合不均匀

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren ...

In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology

Bacterial cells are able to form surface-attached biofilm communities known as biofilms by encasing themselves in extracellular polymeric substances (EPS). The EPS serves as a physical and protective scaffold that houses the bacterial cells and consists of a variety of materials that includes proteins, exopolysaccharides and DNA. The composition of the EPS may change, which remodels the mechanic properties of the biofilm to further develop or support alternative biofilm structures, such as streamers, as a response to environmental cues. Despite this, there are little quantitative descriptions on how EPS components contribute to the mechanical properties and function of biofilms. Rheology, the study of the flow of matter, is of particular relevance to biofilms as many biofilms grow in flow conditions and are constantly exposed to shear stress. It also provides measurement and insight on the spreading of the biofilm on a surface. Here, particle-tracking microrheology is used to examine the viscoelasticity and effective crosslinking roles of different matrix components in various parts of the biofilm during development. This approach allows researchers to measure mechanic properties of biofilms at the micro-scale, which might provide useful information for controlling and engineering biofilms.

In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology

Particle-tracking microrheology investigates the viscoelasticity of materials. Here, the technique is used to determine the viscoelasticity, creep compliance and effective crosslinking roles of different matrix components of a bacterial biofilm. The matrix consists of polymeric substances secreted by the bacteria and its components determine biofilm structure and mechanical properties.

在生物膜的力学性能原位制图粒子追踪Microrheology

Bacterial cells are able to form surface-attached biofilm communities known as biofilms by encasing themselves in extracellular polymeric substances ...

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such as on-demand switchable adhesion technologies, actuators, molecular clutches, and nano-/microscopic mass transporters. Recently it was found that through a special solid-liquid transition, rheological properties can exhibit significant changes, thus providing suitable smart viscoelastic materials. However, designing materials with such a property is complex, and forward and backward switching times are usually long. Therefore, it is important to explore new working mechanisms to realize solid-liquid transitions, shorten the switching time, and enhance the contrast of rheological properties during switching. Here, a light-induced crystal-liquid phase transition is observed, which is characterized by means of polarizing light microscopy (POM), photorheometry, photo-differential scanning calorimetry (photo-DSC), and X-ray diffraction (XRD). The light-induced crystal-liquid phase transition presents key features such as (1) fast switching of crystal-liquid phases for both forward and backward reactions and (2) a high contrast ratio of viscoelasticity. In the characterization, POM is advantageous in offering information on the spatial distribution of LC molecule orientations, determining the type of liquid crystalline phases appearing in the material, and studying the orientation of LCs. Photorheometry allows measurement of a material&#8217;s rheological properties under light stimuli and can reveal the photorheological switching properties of materials. Photo-DSC is a technique to investigate thermodynamic information of materials in darkness and under light irradiation. Lastly, XRD allows studying of microscopic structures of materials. The goal of this article is to clearly present how to prepare and measure the discussed properties of a photorheological material.

This protocol demonstrates the preparation of a photorheological material that exhibits a solid phase, various liquid crystalline phases, and an isotropic liquid phase by increasing temperature. Presented here are methods for measuring the structure-viscoelasticity relationship of the material.

扭曲弯曲的液晶的高对比度和快速光圈开关

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such ...

微流体和 Microrheology 相结合测定软物质在重复相变过程中的流变特性

摘要

探索更多视频

此视频中的章节